Field of the Invention
The present invention relates to an image pickup apparatus that is capable of inserting and extracting a filter.
Description of the Related Art
It is known that an image of an object is blurred due to various factors when an image of an object is picked up with visible light. The various factors include degradation of brightness and rise of darkness (hereinafter referred to as a “contrast variation”) in a video signal that is obtained when an image of an object is picked up, and fluctuation of an object. There is a known image pickup apparatus that takes the blur into consideration and inserts an infrared pass filter of which transmittance for infrared light is higher than transmittance for visible light when the contrast variation in a video signal is detected (for example, see Japanese Laid-Open Patent Publication (Kokai) No. 2012-54904 (JP 2012-54904A)).
Moreover, there is a known image pickup apparatus that inserts an infrared pass filter and picks up an image of an object when fluctuation of the object is detected on the basis of a motion vector of the object in a picked-up image (for example, see Japanese Laid-Open Patent Publication (Kokai) No. 2012-90152 (JP 2012-90152A)). These image pickup apparatuses form an object image by mainly using infrared light, which is hard to be affected by external factors and is highly rectilinear, by inserting an infrared pass filter in order to prevent blur of the object image.
However, an object image may be blurred even if neither a contrast variation nor a motion vector is detected from a video signal. For example, when fog exists between an image pickup apparatus and an object, a sharpness of an object image (difference in brightness at an edge of the object image) decreases because visible light is disturbed by the fog.
As a result, the object image is blurred and quality of the image obtained deteriorates. Moreover, since an influence of the fog that exists between an image pickup apparatus and an object becomes larger as the distance to the object becomes longer, the quality of the image becomes lower with the distance.
Furthermore, there is a case where insertion of an infrared pass filter is not preferable even when a contrast variation or a motion vector is detected. For example, when an image of an object is picked up under low illuminance while inserting an infrared pass filter, an obtained image becomes dark as a whole because the light amount used for forming an image decreases. Accordingly, a gain correction that increases a gain value of an image is applied to the image concerned in order to brighten the image that is dark as a whole. However, a high quality image cannot be obtained because a noise occurs in the image concerned according to the degree of the gain correction.
That is, there is a problem in that the quality of the image obtained deteriorates because the infrared pass filter is not inserted and extracted appropriately.